orient slideshow image caption to left corner

Hello, I would like to orient the captions in my gallery slideshow to be in the bottom left corner of the screen. I used the follow code below, but they still won't go all the way left. I would like them to be farther into the left corner with a little bit of padding from the left side of the screen. thank you in advance! 

.gallery-caption p:first-line {color: white; font-size: 1rem; font-weight:300}

.gallery-caption {text-align:left}

.gallery-caption {
  margin-top: -4%;
  opacity:100!important;}

site pw is flowers 

Thank you for the response and explanation. I am using CSS, however, the code you provided did nothing to alter the caption. The only success I am having is when I change the negative percentage in the margin (in the original code) I would like to only move the caption further left. I tried both with only your code and removed the original code and it still did nothing 😕

Remove your code & Use CSS code like this

figcaption.gallery-caption.gallery-caption-fullscreen-slideshow {
    bottom: 10px !important;
    left: 10px !important;
    margin: 0 !important;
    max-width: 1000px !important;
    height: auto !important;
}